1. Field of the Invention
This invention relates to a process for accurately positioning lead frames onto a ceramic chip carrier to permit wire bonding to the lead frame by means of automatic wire bonding machinery.
2. Description of the Prior Art
In the formation of ceramic chip carriers, lead frames are normally bonded to the ceramic substrate with subsequent connection being made to the leads of the lead frame from appropriate pads in the semiconductor chips secured to the ceramic substrate. These connections from the pads on the chip to the leads of the lead frame are made manually or by means of automatic wire bonding machinery or by mass-bonding techniques using "spider" tape. The automatic wire bonding machinery is normally computer operated on an x-y coordinate basis and it is therefore necessary that the leads of the lead frame be accurately positioned on the substrate so that wiring, which is run from pads on the semiconductor chip to the appropriate lead to the lead frame, is in fact bonded to the appropriate lead of the lead frame.
In accordance with some of the prior art, the entire lead frame was bonded to the ceramic substrate by well known methods and the portions of the leads closely adjacent to the semiconductor device to which wire bonding was to take place would move relative to the semiconductor pads during the process of bonding the lead frame to the ceramic substrate. In the prior art methods, the portion of the lead frame adjacent the chip would be easily distorted in the manufacturing process and lose orientation during bonding to the substrate. It is therefore readily apparent that automatic wire bonding machines can not be used with these types of prior art combination of substrate and lead frame because bonding from appropriate pads of the semiconductor device to the appropriate lead of the lead frame cannot be definitely predicted. It is therefore necessary that a lead frame be bonded to a ceramic substrate wherein the leads of the lead frame are accurately positioned on the substrate and maintain their position during and after the procedure of bonding the lead frame to the substrate.